System and method for peer-to-peer communication in cellular systems

ABSTRACT

Systems and methods are provided for delivering both PMP communications, for example standard cellular communications via a base station, and also delivering P2P communications, for example, communications between two mobile stations, using the same spectral resources for both types of communication.

RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 12/465,304 and claims the benefit thereof, which isa continuation application of U.S. patent application Ser. No.10/815,717, which has issued as U.S. Pat. No. 7,548,758, and claims thebenefit thereof, both of which are incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to peer-to-peer communications and to cellularcommunications.

BACKGROUND OF THE INVENTION

The need for peer-to-peer communication is becoming more prevalent withthe emergence of new applications which involve geographically localizedexchange of information. Currently, the support of cellularcommunications and peer-to-peer communications are enabled by separatesystems, with dual function mobile stations operating exclusively in onemode or the other and utilizing separate spectrum, transceivers, etc.

SUMMARY OF THE INVENTION

According to one broad aspect, the invention provides a mobile stationadapted to participate in wireless PMP (point to multi-point)communications using a cellular spectral resource, the mobile stationbeing further adapted to participate in wireless P2P (peer to peer)communications using said cellular spectral resource.

In some embodiments, said cellular spectral resource comprises adownlink PMP band, and an uplink PMP band, wherein the mobile station isadapted to participate in wireless PMP (point to multi-point)communications using the downlink PMP band for receiving and using theuplink PMP band for transmitting, the mobile station being furtheradapted to participate in wireless P2P (peer to peer) communicationsusing the PMP uplink band for both transmitting and receiving in a TDD(time division duplex) manner.

In some embodiments, a mobile station comprises: a transmitter fortransmitting PMP communications and P2P communications on the uplink PMPband; a first receiver for receiving PMP communications on the downlinkPMP band; a second receiver for receiving P2P communications on theuplink PMP band.

In some embodiments, a mobile station is adapted to listen to PMPcommunications from the network on the downlink PMP band with the firstreceiver for maintenance purposes while transmitting P2P communicationsand while receiving P2P communications with the second receiver.

In some embodiments, a mobile station comprises: transmitter fortransmitting PMP communications and P2P communications on the uplink PMPband; a receiver for receiving PMP communications on the downlink PMPband, and for receiving P2P communications on the uplink PMP band.

In some embodiments, a mobile station is adapted to listen to PMPcommunications from the network on the downlink PMP band for maintenancepurposes only while transmitting P2P communications.

In some embodiments, said receiver is a software defined receiver.

In some embodiments, a mobile station is further adapted to maintainlinked state transitions between states for PMP communications and atleast one state for P2P communications.

In some embodiments, the states for PMP communications comprise dormant,standby and active, and wherein P2P communications are permitted whenthe mobile station is in one of the PMP states dormant and standby.

In some embodiments, a mobile station is adapted to periodicallyinterrupt P2P communications to perform maintenance for PMPcommunications.

In some embodiments, a mobile station is adapted to transition into P2Pcommunications independent of network control.

In some embodiments, a mobile station is adapted to transition into P2Pcommunications independent of network control by directly coordinating asetup of a P2P communications link with another mobile station.

In some embodiments, a mobile station is adapted to coordinate the setupof a P2P communications link with another mobile station by: in responseto a user selection, transmitting a P2P request to the another mobilestation on a P2P access channel; receiving an acknowledgement from theanother mobile station.

In some embodiments, a mobile station is adapted to transmit a frameformat which includes a time slot for PMP communications and a time slotfor P2P communications.

In some embodiments, a mobile station is adapted to transition into P2Pcommunications under network control.

In some embodiments, a mobile station is adapted to transition into P2Pcommunications under network control transparent to a user of the mobilestation.

In some embodiments, a mobile station is adapted to: receive a directionfrom the network to enter P2P communications with another mobilestation; in response to said direction, coordinate set up of P2Pcommunications with the another mobile station; while in P2Pcommunications, listen to PMP transmissions from the network formaintenance purposes.

In some embodiments, both P2P communications and PMP communications areCDMA-like communications.

In some embodiments, a mobile station is further adapted to performsignalling to set up P2P communications with another mobile stationusing an access channel having a defined long code mask announced by anetwork controlling said spectral resource.

In some embodiments, a mobile station is adapted to use a first longcode mask for P2P transmissions to another mobile station, and a secondlong code mask for PMP communications to the network.

In some embodiments, a mobile station is further adapted to perform atleast one of rate control and power control for P2P communications incooperation with the other mobile station.

In some embodiments, a mobile station is further adapted to perform atleast one of rate control and power control for P2P communications undercontrol of the network.

In some embodiments, a mobile station is adapted to initiate P2Pcommunications with a default power, and to request authorization to useadditional power and/or channel resources from the network should P2Pcommunications not be successful.

In some embodiments, a mobile station further comprises at least onesteerable antenna which is steered for use in P2P communication or PMPcommunications.

According to another broad aspect, the invention provides at least onenetwork element adapted to participate in PMP communications with aplurality of mobile stations, the at least one network element beingadapted to: determine when a pair of mobile stations which arecommunicating with each other are sufficiently close together for P2Pcommunications; direct the pair of mobile stations to startcommunicating with each other using P2P communications.

In some embodiments, a cellular network comprises the at least onenetwork element as summarized above.

In some embodiments, the at least one network element comprises a basestation transceiver which determines a pair of mobile stations which arecommunicating with each other are sufficiently close together for P2Pcommunications due to their being located in a coverage area serviced bythe base station transceiver.

In some embodiments, the at least one network element comprises a basestation controller and a plurality of base stations which determine apair of mobile stations which are communicating with each other aresufficiently close together for P2P communications due to their beinglocated in a coverage area of base stations serviced by the base stationcontroller.

In some embodiments, a cellular network is adapted to send and transmitCDMA-like signals.

According to another broad aspect, the invention provides a methodcomprising: a mobile station participating in wireless PMP (point tomulti-point) communications using a cellular spectral resource; themobile station participating in wireless P2P (peer to peer)communications using said cellular spectral resource.

In some embodiments, said cellular spectral resource comprises adownlink PMP band, and an uplink PMP band, wherein the mobile stationparticipates in wireless PMP (point to multi-point) communications usingthe downlink PMP band for receiving and using the uplink PMP band fortransmitting, the mobile station participates in wireless P2P (peer topeer) communications using the PMP uplink band for both transmitting andreceiving in a TDD (time division duplex) manner.

In some embodiments, a method further comprises: the mobile stationlistening to PMP communications on the downlink PMP band for maintenancepurposes while transmitting P2P communications and while receiving P2Pcommunications.

In some embodiments, a method further comprises: maintaining linkedstate transitions between states for PMP communications and at least onestate for P2P communications.

In some embodiments, a method further comprises: receiving a directionfrom the network to enter P2P communications with another mobilestation; in response to said direction, co-ordinating set up of P2Pcommunications with the another mobile station; while in P2Pcommunications, listening to PMP transmissions for maintenance purposes.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described withreference to the attached drawings in which:

FIG. 1A is a schematic diagram of two mobile stations communicating inPMP (point to multipoint) mode;

FIG. 1B is a schematic diagram of two mobile stations communicating inP2P (peer-to-peer) mode in accordance with an embodiment of theinvention;

FIG. 2 is a diagram showing linked state transitions for PMP and P2Pstates;

FIG. 3A shows a mobile station in conventional PMP mode;

FIG. 3B shows two mobile stations communicating in P2P mode usingsoftware defined receivers, in accordance with an embodiment of theinvention;

FIG. 3C shows two mobile stations communicating in P2P mode usingdedicated receivers for P2P communications;

FIG. 4 is an example of a sequence of events leading to independentlyinitiated P2P communications;

FIG. 5 is an example of a sequence of events leading to networkcontrolled P2P communications;

FIG. 6A is an example of a first method of monitoring BS communications;

FIG. 6B is an example of a second method of monitoring BScommunications; and

FIG. 7 shows a super-frame structure providing a third method ofmonitoring BS communications.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the invention provide an efficient means of P2P(peer-to-peer) operation within a cellular system, by reusing thespectrum and some of the transceiver hardware for both modes ofoperation. Some embodiments provide a degree of network control for P2Poperation so as to enable Authentication, Authorization, Accounting(AAA), billing, etc.

P2P operation is particularly beneficial when the users exchanginginformation are within the same geographical area. For example, twousers within a conference room may wish to exchange a file. This cannormally be achieved by utilizing conventional cellular communications,where the file exchange involves the flow of data through the entirenetwork (MS(mobile station)-BS(base station)-BSC (base stationcontroller)-BS-MS if within the same BSC), or utilizing a separate P2Pmode of operation where each user is required to have WLAN (wirelesslocal area network) or alternate hardware that enables such operation ondifferent spectrums. Alternatively, other networks having differentnetwork infrastructure may be employed. For example, for UMTS, the pathmight be UMTS UE-Node B-RNC-GGSN-RNC-NodeB-UE. While the terminologyused below is CDMA specific in some instances, embodiments of theinvention have broader applicability.

In contrast, embodiments of the invention provide a solution where P2Poperation is integrated with the cellular system access. As a result,the overall cellular system efficiency is improved relative to theconventional systems. The use of P2P in place of the first optionintroduced above, i.e. MS-BS-BSC-BS-MS flow, results in a reduced loadon network resources and greater operational efficiency both from thenetwork as well as the terminal perspective (terminals operate at lowerpower to communicate with a user in close proximity). In place of thesecond option above, namely utilizing separate hardware on separatespectrums, the use of P2P integrated with cellular would be moreeconomical, by enabling better spectrum efficiency (reusing cellularspectrum) as well as hardware efficiency (reusing cellular hardware). Inaddition, some embodiments provide the operator with a means to managethe users' P2P communications under the same cellular networkconfiguration for administrative and security functions. Another benefitof having P2P enabled terminals is that the P2P function may come inhandy for emergency situations, such as when a cell site/network goesdown due to a calamity.

The concept of overlaying P2P operation onto a cellular system isillustrated in FIGS. 1A and 1B. Using the conventional cellularspectrum, and with the knowledge of the cellular network, two users mayswitch to P2P operation to exchange files in a P2P enabled cellularsystem, while still maintaining connectivity with the cellular network.

To begin, normal cellular operation is indicated generally by 20 in FIG.1A. Two users are shown with mobile stations 22,24 communicating with acellular network generally indicated by 26 using normal cellularcommunications 28. It can seen that if a significant amount of trafficbetween the two mobile stations 22,24 is to take place, a lot of systemresources would be employed. The P2P mode is generally indicated by 30in FIG. 1B. Here, the two user mobile stations 22,24 communicate witheach other directly as indicated by wireless link 32 which employ thesame spectrum as would be employed for normal cellular operations.Preferably, the wireless links to the network 26 are not entirelydropped, but are used in a maintenance mode 29. The P2P communications32 may be independently controlled by the mobile stations involved withthe communication, and/or can be networked controlled. The P2Pcommunications may be unicast communications in some embodiments, and/ormulticast communications. P2P transmissions may be power and/or ratecontrolled.

Linked State Transitions

In some embodiments, linked state transitions are used to enable bothcellular and P2P communication with the same cellular spectrum and reuseMS resources. A respective state is maintained for cellular (alsoreferred to as point to multipoint, or PMP) operation and for P2Poperation. FIG. 2 illustrates an example of a simplified statetransition scheme, where the state transitions are shown for bothcellular communications(denoted as PMP) generally indicated at 40 aswell as for P2P communications at 42. These state transitions are linkedby state control 53 which is responsible for ensuring PMP operation andP2P operation are functioning together properly.

The states shown for PMP operation include dormant 44, active 46 andstandby 48. These are the standard states defined for cellular operationby CDMA 1×EV-DV standards. When a mobile station is in the active state46, the mobile station is involved with a traffic exchange over thecellular network. The states shown for P2P operation include P2P active50 and PMP dormant 51.

In some embodiments, the PMP active 46 and the P2P active 50 states aremutually exclusive. This means that the PMP state must transition out ofPMP active state 46 before the P2P active state 50 can occur. Similarly,if the mobile station is in P2P active state 50, then it must transitionout of that state in order to go into PMP active state 46.

When the MS enters a dormant 44 or standby 48 state in the cellular modeof operation, it can begin operation in a P2P mode. This involves atransition from either dormant 44 or standby 48 into P2P active 50. ThePMP state of dormant or standby 44,48 is maintained. The mobile stationmay transition out of P2P active state 50 to P2P dormant state 51voluntarily, or alternatively the MS's transition out of P2P activestate 50 may be triggered by the network control. This may for exampleoccur if there is a need to go into PMP active state 46, i.e. if aregular cellular communication is to take place. A P2P buffer 52 may beprovided to retain incomplete P2P transmissions until the nextopportunity for P2P communication arises. In some embodiments, thecellular operation can also be overridden by P2P operation by forcingthe MS into a dormant/standby state 44,48. If this occurs, incompletetransmissions for PMP communications may be stored in a PMP buffer 54.State information and data are stored in separate buffers so as toresume operation when returned to respective P2P or cellular activestate.

The state transition scheme discussed above is a simple design toillustrate the concept. More efficient and/or more complex schemes maybe implemented as appropriate depending on the practical requirements.One of the variants may be to design the P2P states to include multiplestates. Another variant may be to allow best effort based communicationlink in either PMP or P2P mode while engaged actively in the other mode.This needs the maintenance of two or more active sessions at a giventime.

Furthermore, a downlink intensive PMP link could be easily continued asthe mobile station transmitting in P2P mode could listen to the downlinkwhile in P2P mode. Additional states may be defined to implement suchschemes.

All the illustrations below assume the simple state transition schemeproposed in FIG. 2.

Reuse of Cellular Spectrum

Typically, cellular systems operate in FDD (frequency division duplex)mode meaning separate spectrum is used for each of forward link trafficand reverse link traffic. According to the invention, the cellularspectrum is reused for P2P communications. In a preferred embodiment thereverse link cellular frequencies are reused for P2P transmissions.Preferably, the use of uplink also takes advantage of link appropriatemodulation (e.g., long code versus Walsh code in CDMA). This enables thereuse of the reverse link transmitter at the MS. In this embodiment,there needs to be a capability to receive the reverse link transmissionsat a mobile station, something that would not normally be possible. Inone embodiment, each mobile station is further equipped with a reverselink receiver. In another embodiment, each mobile station is configuredto include a software defined receiver (SDRx), and the personality ofthe MS receiver can be changed from FL Cellular Receive to RL P2PReceive mode.

Transceiver Reuse

FIGS. 3B and 3C illustrate two possible options for the MS transceiver.In FIG. 3A, a MS 60 has the conventional transceiver for cellularoperation. This includes Rx PMP functionality 62 for receiving signalsfrom the BS 66, and Tx PMP 64 for transmitting signals to the BS 66.

In some embodiments, at least the receiver is configured to be asoftware defined receiver, as discussed above. In a software definedreceiver, one can change the requisite personalities (carrier frequency,codes, etc.) such that the single receiver can behave either in Rx PMPmode to receive transmissions over the normal downlink frequencies fromthe base station, or in Rx P2P mode during which it receives signalsfrom another mobile station, but on the reverse link frequenciesnormally received by the base station 66. Using the language from thepreviously introduced linked state transitions of FIG. 2, the softwaredefined (SD) receiver operates either in cellular mode when in cellularactive state or in P2P mode when in P2P active state.

FIG. 3B illustrates the transceiver functionality for the embodimentfeaturing a software defined receiver. A first mobile station 70 hastransmit functionality 72 and software defined received functionality74. The transmit functionality 72 may be substantially similar to the TxPMP 64 of the conventional mobile station 60 of FIG. 3A with theexception of the fact that different frame formats may be employed forthe P2P mode as opposed to the PMP mode. FIG. 3B also shows a secondmobile station 76 which is similarly equipped. The two mobile stations70,76 then communicate with each other using the single reverse linkband. Since they are using the same band, the communication must be timedivision duplex. This P2P uplink TDD communication is generallyindicated by 82. This TDD operation is in contrast to the conventionalFDD operation of the mobile station 60 of FIG. 3A, and provides a reasonfor using a different frame format for P2P operation as opposed to PMPoperation. Each of the mobile stations also has a control function. Onlythe control function 71 of FIG. 3B is illustrated.

Depending on a given implementation the scope of the software definedradio functionality may involve changing of MS transmitter parameters tosuit P2P operation on the reverse link in a time divided format. The airinterface configuration for RL Transmit on cellular versus RL Transmiton P2P will be somewhat different in frame formats, since the latterrequires a time division mode of operation on the same RL frequency forboth transmit and receive functions. The RL transmitter needs minormodification to change to the requisite modes for cellular or P2P.Preferably, the MS transmitter always remains on same RL frequency. Thebiggest change involves receiver modifications to allow RL reception inP2P mode from another MS versus FL receive from the BS in cellular,requiring a change of both carrier frequency as well as requiredreceiver processing to match the air interface parameters as needed. Thecarrier frequency changes to the appropriate RL frequency, i.e.,corresponding to the transmitting RL frequency of the peer MS. Note thatif the two MSs are with different frequency carriers or with differentoperators, their UL frequency carriers may be different, and thereceiver has to adapt its receiving frequency to that of the peer MS'stransmit RL frequency.

In another embodiment a transmitter is provided along with an explicitP2P receive chain for P2P operation such as shown in FIG. 3C. Thisalternative has benefits in that one of the receiver chains is alwaystuned to the cellular FL, so as to enable continuous monitoring of thecellular maintenance channels. In some embodiments, the MS antennas aresteerable and the MS directs its antenna appropriately, foroptimizing/enhancing/improving the P2P link or the cellular link to theBS. An example of this is shown in FIG. 3C. Shown is a first mobilestation 90 communicating with a second mobile station 91 using theuplink frequencies in TDD mode. The first mobile station 90 has separatereceiver hardware 92 for receiving in Rx PMP mode, and separate hardware94 for receiving in Rx P2P mode. The mobile station 90 also hastransmitter 96. In some embodiments, the transmitter may be softwaredefined at least to the extent that different frame formats areconfigurable so as to allow both P2P and PMP activities. Similarly, asecond mobile station has Rx PMP hardware 98, transmit functionality 100may be at least partially software defined, and Rx P2P functionality102.

The illustrations of FIGS. 3B and 3C are highly abstract. A given mobilestation will of course be equipped with any hardware and/or softwarerequired to enable the mobile station to participate in its regular PMPcommunications. This hardware and/or software will vary depending uponthe particular type of PMP communications involved. In some preferredembodiments, the PMP communications are CDMA communications, for exampleas defined in any one of a number of CDMA standards including, but notlimited to 1×EV-DO, 1×EV-DV, UMTS HSDPA. Typical functionality willinclude transmitter, receiver and a control function, and of course userinterface functions such as speaker, microphone, etc. Most of thisfunctionality is not relevant to the invention and has been omitted fromthe figures and description in the interest of clarity. The controlfunction in a conventional mobile station is responsible for maintainingthe state of the mobile station, for example the enhanced control hold,dormant and active states for 1×EV-DV described above with respect toFIG. 2. In mobile stations provided by the invention, the controlfunction is expanded to include the additional ability to switch betweenP2P mode, PMP mode, and to control the PMP mode. This additional controlfunctionality may be implemented by modifying existing control functionsoftware, and/or by providing additional hardware and/or software. Thecontrol function might for example be implemented as a microprocessor orFPGA, either generic or custom, together with software and/or firmware.However, any appropriate control implementation is contemplated.

P2P Operation

In one embodiment, P2P operation between MSs is independent userinitiated P2P communications without BS involvement in establishing theP2P connection. This does not require P2P users to be communicating withthe same BSC (e.g., users in the same room may be connected to differentBSCs).

In another embodiment P2P operation between MSs is network controlled.In this embodiment, the network leverages the P2P feature to improveradio resource efficiency, when it detects those users exchanging dataare within the same BSC area. The level of network control, and thelimitations imposed by network control may differ from oneimplementation to another. For example, in a cellular network which hasa network infrastructure different from the MSC (mobile switchingcentre), BSC, BTS hierarchy employed in the embodiments describedherein, there may be different limitations on when two mobile stationsare permitted to communicate in P2P mode.

It is contemplated that a given implementation may allow bothindependent and network controlled P2P operation, or just one ofindependent and network controlled P2P operation.

P2P Operation in Independent Mode

As discussed above, with independent P2P mode collocated or close by MSscan initiate P2P operation in a cellular system which has P2P enabled.For this purpose, a P2P access channel is provided through which theusers may attempt to establish initial P2P link setup. Preferably, thisP2P access channel is defined as part of the system's air interface.Once a MS receives a request for a P2P connection from another MS, itcan acknowledge the request, and a power requirement assessment processis invoked by both the mobile stations. This may be as simple as settingup the P2P connection using a default power setting. For this purpose,preferably a maximum power limit much lower than the normal uplinktransmit power is provided to a mobile station. This is possible becausetwo mobile stations operating in P2P mode will always be much closertogether than the maximum distance between a mobile station and a basestation which are communicating together each in standard cellularcommunications. In some embodiments, if communication fails using adefault power and channel resources, one or both of the MSs could make arequest from the network to obtain a higher power quota and/oradditional channel resources, and establish a link as indicated underthe network control mode discussed below. If direct communication failseven in this mode, the mobile station may decide to communicate usingthe cellular mode.

Assuming the simple state transition diagram of FIG. 2, the MSs canattempt a P2P connection while in dormant or standby state. It is ofcourse to be understood that the state transition diagram of FIG. 2 isbut one example. Depending upon the state transition diagram for a givenimplementation, there may be different sets of states during whichmobile stations can or cannot attempt P2P connections.

FIG. 4 illustrates an example of the operation in the independent mode.MS B 102 actively listens to P2P control channel for P2P request 105from MS A 100. When it detects MS A's address it responds with an ACK106. Following acknowledgement 106, the two mobile stations MS A 100 andMS B 102 then communicate with each other in P2P mode as indicated at108. Preferably, the MSs periodically return to the original cellularstate (Dormant/Standby) for maintaining the cellular connection (e.g.,sync, paging channel). This is illustrated in the example of FIG. 4 withPMP maintenance 110 between MS A 100 and the base station 104, and PMPmaintenance 112 between MS B 102 and the base station 104.

A very specific signalling example for independent P2P operation hasbeen described with respect to FIG. 4. The various messages may be sentusing any appropriate mechanism such as an access channel for P2Poperation. More generally, the signalling performed between two mobilestations to set up P2P operations may very from one application toanother and is certainly not limited to the particular example of FIG.4. In this case, there is no direct involvement of the network in theP2P operation. The access channel could be a common channel similar tothe RACH in 3GPP systems. However any appropriate access channel iscontemplated.

Independent P2P Operation Example

The following steps illustrate a detailed example of the independent P2Poperation assuming the users are able to communicate with a defaultpower level available for the P2P independent mode discussed above. Inthis example, it is assumed that P2P mode communications are initiallyset up, and then a first mobile station followed by a second mobilestation are respectively transitioned from P2P operation to PMPoperation and back again. The purpose of this example is to show how acellular mode connectivity may preempt P2P mode activity. It is ofcourse to be understood that in a given operational scenario, thesequence of events described below will not necessarily take place sincethis assumes the particular scenario where in the first mobile stationis interrupted followed by the second mobile station. The examplesequence of events follows:

-   -   1) Both users switch to P2P mode for file exchange; 2) mobile        stations MS A and MS B listen to P2P access channel;    -   3) when successful, mobile stations perform handshake;    -   4) users commence communication in P2P mode:        -   a) MSs receiver retunes to RL frequency channel;        -   b) MSs communicate with each other over RL frequencies at            low power; and        -   c) MSs operate on RL in TDD mode;    -   5) MSs continue to maintain cellular mode connectivity;    -   6) MS A is interrupted by a FL transmission request:        -   a) MS A stops P2P communication with “pause” message to MS            B;        -   b) excess P2P data packets are stored in P2P data buffer in            MS A and MS B; and        -   c) MS A returns to cellular active state;        -   d) when MS A returns to FL Standby or dormant state (more            generally, when MSA no longer requires resources for regular            cellular communication, and is available again for P2P mode            communications), reattempts connection to MS B on P2P access            channel;        -   e) meanwhile, MS B has entered cellular active state;        -   f) MS A continues to reattempt P2P access;        -   g) MS B returns to Standby/dormant; resumes P2P attempt;        -   h) MS A and MS B resume P2P mode until action is completed;        -   i) users turn off P2P mode until next needed; and        -   j) MSS return to normal cellular mode operation.

In the example above, it is assumed that the regular cellular modeactivity will take precedence over P2P mode activity. In someembodiments, it will be a user configurable parameter, either on anongoing basis or on a per use basis, which stipulates which type ofconnectivity takes precedence. In this way, users may switch to P2P modeand complete a file transfer without repeatedly being interrupted forcellular communications.

Preferably the mobile stations periodically retune to the regularcellular downlink communications frequencies to enable them to listen toconventional base station commands for example while in the standby ordormant state. The mobile stations can also use the uplink channel totransmit maintenance messages to the base station. Depending upon agiven implementation, different mechanisms may be employed todistinguish between uplink transmissions to the base station, andtransmissions using the uplink frequencies to another mobile station inP2P mode. Examples are given below for CDMA systems, but alternativemeasures may be employed to achieve this effect.

P2P Operation in Network Controlled Mode

In these embodiments, the network is in control of P2P mode. In oneembodiment, the BS itself makes the decision to initiate P2Pcommunications between two MSs triggered by realizing the benefits ofP2P operation between 2 MSs exchanging data within its cell, or inadjacent cells in the BSC. If the user locations within the cell areavailable, the network correlates this information with users connectedto each other within the cell(s). The network advises users to attemptconnection by allocating a P2P access channel for this purpose. When theusers report a successful handshake, the network transfers the users toP2P mode.

In network controlled mode, the network is responsible for making thedecision for two mobile stations to enter P2P mode. Depending upon agiven network implementation, this decision may be made by any number ofnetwork elements. For example, in a network featuring the aboveintroduced MSC, BSC, BTS hierarchy, this responsibility might rest withthe BSC which would allow P2P communications between MSs located indifferent cells, or with the BTS which would restrict P2P communicationsto be within a given cell. However, the network infrastructure forcoordinating this may rest in a single network element or in acombination of network elements. In preferred embodiments, the onlychange to existing networks is to introduce a few additional signalingmessages to enable the network to instruct MSs to enter P2P mode.Examples of a few such messages are given below in FIG. 5, but these areonly a particular example. It is to be understood that many methods of anetwork coordinating two MSs to enter P2P mode may be implemented withinthe scope of the invention insofar as network controlled P2P isconcerned. Preferably, this additional messaging is implemented as anextension to existing software and/or hardware which is providing thecellular connectivity and control.

For embodiments which make use of location information, various existingtechniques may be used to determine the mobile station location. Forexample, most systems currently do have some location determiningability to enable 911 services. Furthermore, if a mobile station isactive within the network, it will be possible to know which cell themobile station is operating in. Other methods of determining mobilestation are also contemplated. For example, mobile stations equippedwith GPS technology may inform the network of their locations. Thedetails of the mechanism for determining the location of the mobilestations are outside the scope of this invention.

Preferably, for embodiments featuring network control, some form ofpower control is implemented to ensure that P2P communications do notinterfere with other communications. It may at the same time be possibleto increase power to a level which might provide enhanced performance.In one embodiment, a basic default power limit is prescribed by thenetwork.

If the MSs fail to access each other directly with the basic powerlimits allocated for this mode, in some embodiments they may request forexclusive power levels and/or other resources such as exclusivechannels, to establish the communication link. It should be noted thatthese specific resources are only for one way communication and theresources are the reverse link resources. Depending on the mobilelocation, higher rates could be used by the mobile stations for directcommunication and as such, even with this reverse link allocation, P2Pmode can lead to significant savings in the resources.

If the mobile stations fail to establish a good communication link evenafter these grants, the network continues the standard cellular mode ofoperation. Note that in preferred implementations all of these actionsare transparent to the users.

If the communication fails after establishment of the P2P mode due tofading of signals or movement of the mobile stations, they may beswitched back to the cellular mode immediately.

FIG. 5 illustrates an example of the network controlled P2P operation.This example of P2P operation assumes the users are able to communicatewith a default power level specified for this purpose. This exampleshows P2P communications between a first mobile station 120, hereafterMS A and a second mobile station 122, hereafter MS B as coordinated by abase station 124. The operation begins with the base station sending amessage to each of the two mobile stations 120,122 recommending thatthey transition into P2P mode operation. In the illustrated example,this is shown as P2P request message 126 from BS 124 to MS A 120, andP2P request message 128 from the BS 124 to MS B 122. In response tothese messages, the mobile stations 120,122 attempt to connect via P2Pas indicated at 130. In the event there is success, the two mobilestations 120,122 send respective messages to the base station 124 toindicate success. In the illustrated example, this consists of P2Presponse messages 132,134. In response to this, the base station 124acknowledges the response messages with begin P2P message 136 to MS A120 and begin P2P message 138 to MS B 122. Following this, the mobilestations 120,122 proceed with P2P communications as indicated at 140.Preferably, both mobile stations 120,122 periodically return to theoriginal cellular state (for example dormant or standby) for maintainingthese cellular connections (for example for synchronization timing, etc.and for receiving paging messages). In the network control operationalmode, preferably all of these operations are transparent to the user.

Maintaining Cellular Connectivity

Preferably, P2P capable MSs return to cellular mode for cellular linkmaintenance so as to be in a position to respond to any commands fromthe cellular network, such as a page. Various methods of achieving thismaintenance function will be described below, but other methods may beused without departing from the scope of the invention.

FIGS. 6A and 6B illustrate examples of behavior of two MSs when in P2Ptransmit or receive mode. Two different examples of behaviour will begiven, one for the case where the mobile stations have software definedreceivers, as described previously with respect to FIG. 3B, and anotherfor use in the case where receivers have separate receiver hardware forP2P mode communications and PMP mode communications, as describedpreviously with respect to FIG. 3C. In FIG. 6A, two MSs 150,152 eachhave a respective single software defined receiver 154,156 which canadapt to receiving either FL (cellular) or RL (P2P). While an MS in P2Ptransmit mode can still receive the FL, an MS in P2P receive mode cannotdo so. In the example of FIG. 6A, mobile station 152 is in transmitmode, and it has its software defined receiver 156 tuned to monitor theforward link from the base station as indicated at 158. At the sametime, the mobile station 150 has its software defined receiver 154 tunedto listen to reverse link transmissions from the other mobile station152. Because of this it is unable to listen to the forward link from thebase station. Mobile station 152 has an active transmitter while thetransmitter 162 of mobile station 150 is idle. These roles all reversein a time division duplex manner such that during the next time slot,the mobile station 150 is capable of monitoring the forward link fromthe base station and the software defined radio of mobile station 152 islistening to the transmissions of the other mobile station 150 and assuch is unable to listen to the base station. In another embodiment aslotted mode, described below, is provided as a solution to enable thereceiving MS to still monitor the cellular channel.

In the example of FIG. 6B, the two mobile stations 170,172 haverespective transmitters 174,184, have respective receivers 176,182 forcellular mode communications (i.e. PMP mode) and have respectivereceivers 178,180 for P2P mode communications. Advantageously, with thisembodiment, the FL receive chain can continuously monitor the FL channelfrom the BS, in which case the above-referenced slotted mode of P2Ptransmission is not necessary.

One manner of realizing a slotted mode operation so as to enable the P2Preceiving MS to perform dormant/standby state maintenance functions(e.g., monitor paging channel) is to introduce a super-frame structure,where a fraction of this super-frame is used for P2P operation.

FIG. 7 illustrates an example of a super-frame structure for enablingthe monitoring of the cellular channel when in P2P mode. The super framestructure 200 of FIG. 7 has two periods, a first period 202 during whichP2P communications are enabled, and a second period 204 during whichregular cellular operations are enabled. The P2P operation may bethrottled by the paging needs of the receiving MS, and thus P2Poperation may be interrupted once every paging period. Preferably, apaging request from the BS to the MS will result in an access channelmessage exchange between the 2 MSs to pause the P2P operation, so as torespond immediately to the page and initiate a cellular conversation.

Achieving Synchronization in P2P Mode

In TDD, mobile stations send and receive alternatively; each mobilestation gets a chance to transmit during which, in some embodiments, itcan listen to the base station (Forward link). The time spent in Tx modewill depend on the application type and the protocol it uses. Since P2Ptransmission is done in a time divided format on the reverse link, whena mobile station transmits in P2P mode using the RL frequency, itsreceiver can listen to the base station (FL frequency) forsynchronization.

For example, assume MS A initiates the P2P connection and startstransmission to MS B. MS A's receiver still can listen to the basestation using the FL frequency and will continue to maintainsynchronization. MS B's receiver changes from FL Rx mode to RL Rx modeMS B will only lose synchronization if it operates on P2P Rx mode for along duration.

Additionally, while MS A is transmitting on the regular RL and remainssynchronized by listening on the FL, MS B can use MS A as an alternatefrequency reference. This depends on MS Tx timing within necessarytolerance, and MS keeping track of 2 timing offsets (system and peer).

Power and Rate Control

Cellular systems employ either rate control or power control for theBS-MS link, so as to maximize spectrum efficiency and minimizeinterference. In some embodiments power control and/or rate control arealso applied on a P2P connection.

Many options for power and/or rate control exist which are wellunderstood by those skilled in the art. In one option, there is no powercontrol, but rather there is simply a fixed power for P2Pcommunications. Either a fixed modulation and code is used or AdaptiveModulation and Coding (AMC) is employed for rate control. In anotherembodiment, rate control has a fixed initial rate which isconservatively selected, and this is followed by an open loop type ofquality measurement upon which rate control adjustments are employed. Inanother embodiment, slow power control is employed. Full power controlas in the cellular communications systems may alternatively be employed.A combination of rate control and power control may be employed in whichallocated power (allocated for example on the basis of closed loop powercontrol) is used in conjunction with rate control.

Link Reliability and Interference

In the independent mode, the P2P link reliability may be maintained insome embodiments by MS measuring the interference levels before enteringP2P mode to decide whether to transition into P2P mode and also; duringP2P mode, to decide whether to perform discontinuous transmission (DTX)or to switch back to PMP.

In some embodiments, power and/or rate control are employed, and P2Pmode is entered only when proper proximity of users is available.

It is noted that low power transmission within a conference room orcontained area may cause negligible RL interference at the cell site.However, a strong nearby interference will limit P2P operation.

In the network controlled mode, the BS may assign the transmit powerlevel as a grant for P2P operation. Since the transmission is managed bythe BS, there is no expected operational impact on the system.

The described embodiments assume cellular connectivity is maintainedeven while in independent P2P mode. The cellular connectivity is usedfor maintaining synchronization and also to service cellular calls.

In another embodiment, P2P mode can also be considered as workingindependent of the cellular mode to support public safety and emergencycalls or calls outside the cellular range. To support this application,a model is employed which enables P2P MSs to operate in, a master-slaverelationship with some form of sync messaging, such as by using amodified pilot channel, or the use of a frame format with a specificdata sequence to identify the start of a frame. This mode of operationmay be enabled by manually entering a separate mode wheresynchronization is established locally rather than with the help ofnetwork control. Alternately, GPS availability in mobile stations willenable the maintenance of sync without connectivity to the cellularnetwork.

For P2P to operate completely independent of the cellular network, butstill utilize the licensed cellular spectrum, there may be issues withrespect to operation in licensed cellular bands in regions that theoperator does not necessarily own or have roaming agreement with.

Support of multiple service instances may need special considerationsfor P2P operation. If we use the simple state transition diagramdescribed above, the system can go to P2P mode only when both PMPsessions are in dormant or standby mode. However, with a more efficientMAC state design, P2P may be implemented with a relative priorityassigned to transmissions in each mode. For example, P2P may be operatedon a best-effort basis or all of some of the PMP services may operate onthe best effort basis, etc.

Example of Independent Mode Specific to CDMA System

The example begins with one or more users switching voluntarily to P2Pmode for file exchange and listen to P2P access channel.

Preferably, a universal access channel (P2P access channel, shared byall cells) is dedicated to P2P operation. A CDMA long code mask and apower limit of this channel is broadcast by the network (for example byBSs) to all MSs.

All MSs involved in P2P operation listen to the P2P access channel andattempt to check if there is a setup request for it.

Collision is possible for this P2P operation and preferably some kind ofcollision resolution is provided (e.g., back off). The P2P data can betransmitted after a negotiation for example as in 802.16.

The P2P access channel is then used for initial setup and exchange of aprivate long code MASK specifically used by the group of P2P MSs. Thisallows the P2P communications to be distinguished from PMPcommunications.

After successful P2P handshake, P2P MSs exchange data on the uplinkfrequencies with the specifically agreed private long code mask. Thepower level for the P2P operation may be a network parameter set to beat some very low value so as to minimize interference from P2Poperation. Preferably, some simple form of rate control and/or powercontrol can be implemented to manage the link more efficiently.

In order to receive the CDMA P2P signal, a MS searches the P2P accesschannel by using a searching window which might, for example, span up to2×T_(one-way-delay) centered on the action time

-   -   Note: T_(one-way-delay) is the maximum one-way delay determined        by the cell size;    -   Multiple search windows may be maintained in a table lookup if        multicast mode is used.        Preferably MSs periodically (determined by PMP state) return to        PMP mode for PMP link maintenance.

For example a super-frame structure such as described above may bedefined and a fraction of this super-frame is used for P2P operation.This is to enable the MS to perform its dormant/standby statemaintenance functions (e.g., monitor paging channel).

Example of a Network Controlled Mode Specific to CDMA System

A CDMA BS identifies two MSs within its cell that are exchanging dataand decides to attempt transfer to P2P mode. The BS notifies both MSs toattempt P2P link on an assigned P2P access channel and continuesprocessing the MSs data while it waits for MS response. If both MSssuccessfully complete the handshake, the MSs report a success. The BSsends a P2P-ACK which indicates to MSs they can continue theircommunication on the P2P link. BS may allocate nominally higher transmitpower level for specific P2P operation. MSs move to dormant/standbystate on the PMP link, and switch transmissions to the P2P link.Communication continues as in independent mode. Search window operationand PMP link maintenance may be performed as with independent mode. P2Pcommunications may be preempted by a BS message or a weakening of theP2P link, when the MSs can switch back to PMP mode. P2P and PMP messagebuffers are coordinated so as not to lose any data during thetransitions.

While the illustrated function for a CDMA system, this does not precludethe design to be applied to other standards, such as OFDM.

In some embodiments, when the cellular subscriber powers up there is theautomatic registration process to the network which performs theAuthorization, Authentication and Accounting functions. Following this,independent P2P communications are also protected by the exchange of aprivate long code mask for the specific data exchange.

Numerous modifications and variations of the present invention arepossible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described herein.

1. (canceled)
 2. An apparatus, comprising: an integrated circuitconfigured for inclusion in a first mobile station, wherein theintegrated circuit is configured to: provide a synchronization messagefor synchronization on a cellular frequency band to a second mobilestation while the second mobile station is out of range of a cellularbase station operating on the cellular frequency band; transmit andreceive first wireless communication information directly to a secondmobile station on the cellular frequency band while the second mobilestation is out of range of the cellular base station; transmit andreceive second wireless communication information directly to a thirdmobile station on the cellular frequency band when in range of thecellular base station operating on the cellular frequency band; andtransmit third wireless communication information directly to thecellular base station on the cellular frequency band when in range ofthe cellular base station operating on the cellular frequency band. 3.The apparatus of claim 2, wherein synchronization is maintained with thecellular base station.
 4. The apparatus of claim 2, wherein theintegrated circuit is further configured to transmit signaling to thesecond mobile station to identify the start of a frame.
 5. The apparatusof claim 2, wherein the integrated circuit is further configured totransmit a first direct transmission to at least one of the second orthird mobile stations for direct communication establishment, whereinthe first direct transmission is transmitted in a first set of definedresources, wherein the first set of defined resources are defined forfirst transmissions for direct communication establishment.
 6. Theapparatus of claim 5, wherein the first set of defined resources isindicated by the cellular base station.
 7. The apparatus of claim 2,wherein the integrated circuit is further configured to receive aconfiguration of a first portion of time for which directmobile-station-to-mobile-station transmissions for the first mobilestation are enabled and a second portion of time for whichmobile-station-to-cellular-base-station communications are enabled. 8.The apparatus of claim 2, wherein the integrated circuit is furtherconfigured to inform the cellular base station of a geographicallocation of the apparatus to assist in allocation of resources fordirect communication.
 9. The apparatus of claim 2, wherein theintegrated circuit is further configured to transmit a request to thecellular base station for resources for direct communication.
 10. Amobile station, comprising: one or more antennas; and an integratedcircuit configured to communicate via the one or more antennas, whereinthe integrated circuit is further configured to: provide asynchronization message for synchronization on a cellular frequency bandto a second mobile station while the second mobile station is out ofrange of a cellular base station operating on the cellular frequencyband; transmit and receive first wireless communication informationdirectly to a second mobile station on the cellular frequency band whilethe second mobile station is out of range of the cellular base station;transmit and receive second wireless communication information directlyto a third mobile station on the cellular frequency band when in rangeof the cellular base station operating on the cellular frequency band;and transmit third wireless communication information directly to thecellular base station on the cellular frequency band when in range ofthe cellular base station operating on the cellular frequency band. 11.The mobile station of claim 10, wherein synchronization is maintainedwith the cellular base station.
 12. The mobile station of claim 10,wherein the integrated circuit is further configured to transmitsignaling to the second mobile station to identify the start of a frame.13. The mobile station of claim 10, wherein the integrated circuit isfurther configured to transmit a first direct transmission to at leastone of the second or third mobile stations for direct communicationestablishment, wherein the first direct transmission is transmitted in afirst set of defined resources, wherein the first set of definedresources are defined for first transmissions for direct communicationestablishment.
 14. The mobile station of claim 13, wherein the first setof defined resources is indicated by the cellular base station.
 15. Themobile station of claim 10, wherein the integrated circuit is furtherconfigured to receive a configuration of a first portion of time forwhich direct mobile-station-to-mobile-station transmissions for themobile station are enabled and a second portion of time for whichmobile-station-to-cellular-base-station communications are enabled. 16.The mobile station of claim 10, wherein the integrated circuit isfurther configured to inform the cellular base station of a geographicallocation of the mobile station to assist in allocation of resources fordirect communication.
 17. The mobile station of claim 10, wherein theintegrated circuit is further configured to transmit a request to thecellular base station for resources for direct communication.
 18. Amethod of operating a mobile station, comprising: providing asynchronization message for synchronization on a cellular frequency bandto a second mobile station while the second mobile station is out ofrange of a cellular base station operating on the cellular frequencyband; transmitting and receiving first wireless communicationinformation directly to a second mobile station on the cellularfrequency band while the second mobile station is out of range of thecellular base station; transmitting and receiving second wirelesscommunication information directly to a third mobile station on thecellular frequency band when in range of the cellular base stationoperating on the cellular frequency band; and transmitting thirdwireless communication information directly to the cellular base stationon the cellular frequency band when in range of the cellular basestation operating on the cellular frequency band.
 19. The method ofclaim 18, further comprising: maintaining synchronization with thecellular base station.
 20. The method of claim 18, further comprising:transmitting signaling to the second mobile station to identify thestart of a frame.
 21. The method of claim 18, further comprising:transmitting a first direct transmission to at least one of the secondor third mobile stations for direct communication establishment, whereinthe first direct transmission is transmitted in a first set of definedresources, wherein the first set of defined resources are defined forfirst transmissions for direct communication establishment.